Defrosting means



Feb. 10, 1942. H. J. KRACKOWIZER DEFROSTING MEANS Filed May 5, 1939 3SheetsSheet 1 WWW w I I Q I I I 1942' I H. J.- KRACKOWIZER 2,272,302

DEFROSTING MEANS Filed May 5, 1939 '3 Sheets-Sheet 2 ag e Feb. 10, 1942.H. J. KRACKOWIZER 2,

DEFROSTING MEANS Filed May 5, 1939 3 Sheets-Sheet 3 if 5/ W 50 f0Patented Feb. 10, 1942 UNITED STATES PATENT OFFICE DEFROSTING MEANSHermann J. Krackowizer, Chicago, 11].

Application May 5, 1939, Serial No. 271,833

5 Claims.

My invention relates to refrigerating equipment wherein air is cooled bycirculation through a cooling unit and has reference more particularlyto improved means for removing frost which may accumulate on the coolingunit.

In refrigerating equipment of the type above referred to, moistureoftentimes condenses out of the circulated air and freezes onto thesurfaces of the cooling unit and it is necessary to remove the frostoccasionally. This is usually accomplished by shutting off therefrigerating mechanism until the cooling unit and the surrounding airwarm up sufiiciently to melt the frost, although such defrostingprocedure is objectionable not only on account of the length of timerequired during which cooling is interrupted, but also because thetemperature in the compartment or other space normally cooled by therefrigerating device is elevated during the defrosting period and thisnot only imperils the preservation of any perishable contents of thecompartment, but requires prolonged operation of the refrigeratingmechanism and imposes extra load thereon after the defrosting to restorethe normal low temperature of the compartment or other space which waslost during the defrosting.

The principal objects of my invention are to provide improved defrostingfacilities; to minimize the time required for defrosting; to accomplishthe defrosting without affecting the temperature of the compartment orspace which is normally cooled by the refrigerating device; to avoidprolonged operation of or extra load on the refrigerating mechanismafter defrosting; and to provide simple and convenient defrostingfacilities which avoid the disadvantages previously experienced indefrosting and increase the efficiency of refrigerating equipment--theseand other objects being accomplished as pointed out hereinafter and asshown 'in the accompanying drawings in which:

Fig. l is a vertical section taken lengthwise through a cooling deviceconstructed in accordance with my invention;

Fig. 2 is a view showing somewhat diagrammatically a compartmentequipped with the cooling device of Fig. 1;

Fig. 3 is a side view of the cooling device;

Fig. 4 is a section taken on the line 44 of Fig. 3;

Fig. 5 is a detail view showing a gate for closing a passage at the sideof the cooling unit;

Fig. 6 is a sectional view taken on the line 6-5 of Fig. 1;

Fig. 7 is a side view of the cooling unit taken on the line l'| of Fig.6; and

Fig. 8 is a diagrammatic view of the refrigerating mechanism andcontrols.

In refrigeration it is a common practice to employ a cooling unitthrough which air is circulated for cooling a compartment or otherspace, the cooling unit usually consisting of coils to which compressedrefrigerant is supplied through an expansion valve so that it evaporatesand expands in the coils, thereby absorbing heat, after which it iswithdrawn by a compressor and after recompression is returned throughthe expansion valve to the coils.

Such cooling units ar employed for various purposes as for example forcooling compartments in which perishable goods or articles are kept at asufficiently low temperature to preserve same or for air conditioningrooms of buildings in which people live or congregate. Controls areusually provided to cause intermittent operation of the refrigeratingdevice at suitable intervals and for proper lengths of time to maintainthe refrigerated compartment or air conditioned room at a selected ordesired temperature, a fan being ordinarilyemployed to circulate airthrough the cooling unit and discharge same into the compartment or roomand usually serving also to withdraw air from the compartment or room sothat it is recirculated through the cooling unit.

In the accompanying drawings which illustrate the application of myinvention to a cooling device for cooling a refrigerator compartment,the reference numeral H (see Fig. 2) indicates the compartment which hasthe cooling device, indicated as a whole at I2 near the ceiling l3 atone side or end. This cooling device comprises a cooling unit composedof coils M to the inlet l5 of which refrigerant is supplied in the usualmanner from a compressor 16 (see Fig. 8) through an expansion valv I lwhich is controlled by a bulb 18 secured to the cooling unit near theoutlet l9 which is connected to the intake sid of the compressor I6,said bulb I8 being operatively connected with the expansion valve in theusual manner by the tube 20.

The expansion valve I1 is located adjacent to the cooling unit, and hasa supply pipe 2| leading thereto and provided at its outer end with acoupling 22 by which it is detachably connectible with the outlet of thecompressor, which is usually located at a remote place outside thecompartment II; and the outlet [9 also has a coupling 23 at the outerend for detachable connection with the intake of the compressor, itbeing understood of course, that the inlet and outlet of th cooling unitmay not lead directly to the outletand intake respectively of thecompressor but are connected therewith through the usual intermediateappurtenances with which refrigerating systems are ordinarily provided.

The coils I4 are mounted in the usual end plates 24 and 25, which serveas hangers for supporting the cooling unit, with the return bends 25 ofthe coils and other connections at the outer sides of these plates 24and 25, and the portions of the coils I4 between the plates 24 and 25have the usual fin plates 2'! thereon for increased heat conductivity. Afan 23, operated by an electric motor 29 is mounted to dischargedthrough the" cooling unit, that is, through the spaces between the coilsI4 and fin plates 21, and is preferably located in the opening 30 of aplate 3| which has side wings 32 by which it is attached as at 33 to theend plates 24 and 25 of the cooling unit.

Brackets 34 secured at intervals around the opening 30 support the motor29 so that the fan 28 is located in said opening.

This cooling unit and fan assembly is mounted in a housing or box whichhas top and bottom walls 35 and 36 respectively, side walls 31 and awall 38 at one end. the other open end of said housing being adapted tobe closed by a door 39 which is hinged at 40 to the top wall 35 and atthe other or closed end of the housing there is an opening 4| throughthe bottom adapted to be closed by a door 42 which is hinged at 43 tothe end wall 38. All of the walls and doors of this housing are heatinsulated as indicated at 44' so that when the doors 39 and 42 areclosed a heat insulated compartment is provided containing the coolingunit and fan assembly which'is located in thecompartment as shown inFigs. 1

and 4 so as to discharge toward and through the open end of thecompartment when the door 39 is open and against said door when thelatter is closed, while the bottom opening 4| at the other end of thecompartment provides an in take opening for air to be circulated throughthe cooling unit when the door 42 is open.

These doors 39 and 42 are connected in any suitable manner to close andopen simultaneously, this being accomplished in the present structure byproviding a lever 45 which is pivoted centrally at 46 to a side wall 31and has one end connected by a link 41 with the door 39 and the otherend connected by a link 48 with the door 42 as shown particularly inFig. 3 so that closing either door swings the lever 45 to the uprightposition thereby swinging the other door simultop wall 35 with aperturedends projecting at;

opposite sides of the housing to accommodate bolts50 by which thehousing is suspended'from the ceiling of the compartment II and the topwall 35 in turn supports the assembled cooling ,unit and fan. the endplates 24 and 25 of the cooling unit being provided for this purposewith outturned flanges 5| at their upper ends which are secured to thetop wall 35 by bolts 52, each end plate 24 and 25 preferably having oneof its mounting bolts 52 engaged through the channel iron 49 thereabove.

This cooling unit is located close to the top 4 wall 35 of the housingand spaced from the bottom wall 36 suiliciently to accommodate a drainpan 53 which rests on the bottom wall 35 and has a lip 54 engaged overthe margin of the front door opening of the housing to hold the pan inplace, and this pan has a drain tube 55 extending therefrom to theexterior of the housing and leading outwardly through a wall of thecompartment II or to other convenient place for discharge of drainagefrom the pan 53, the portion of the drain tube 55 outside the fan andcooling unit housing being preferably covered with insulation asindicated at'55.

The end plates 24 and 25 of the cooling unit are spaced from the sidewalls 31 of the housing as indicated at 56 and 51 respectively toaccommodate the return bends 2B of the coils, the space 55 alsocontaining the expansion valve l1 and the pipes l5 and 2|, the latter ofwhich as well as the outlet pipe l9 having their ends with theirrespective couplings 22 and 23 projecting through said side wall.

In the normal operation of this cooling device, the doors 39 and 42 areopen and the fan 28 operated so as to draw air from the compartmentthrough the bottom opening 4| into the housing wherein it is propelledby the fan through the cooling unit and discharged through the openfront end of the housing back into the compartment at the top thereof.

The cooling unit is cooled in the usual manner to absorb heat from theair circulated therethrough, by operation of the compressor I6 whichsupplies compressed refrigerant through the expansion valve H to thecoils M in which the compressed refrigerant is evaporated or expandedand then returned to the compressor to be compressed again andrecirculated through the system, it being customary to provide controls,responsive to the temperature in the compartment, for operating thecompressor intermittently at suitable intervals and for varying lengthsof time as required to maintain the compartment at a selected or desiredtemperature.

A motor, indicated at 58 in Fig. 8, is usually employed for operatingthe compressor l6 and the required intermittent operation of thecompressor may be effected by a switch through which current is suppliedto the motor, the switch in turn being operated by a thermostat in thecompartment or by a pressurestat in the refrigerant circulating systemor in any other convenient manner.

For illustrative purposes I have shown in Fig. 8 a pressurestat controlwhich is well known and comprises a pressurestat 59 which is connectedwith and responsive to variations of pressure in the expansion or lowside of the refrigerating system and operates a switch 60. Conductors BIand 62 lead from a source of electric power (not shown) to the motor 58,said switch 60 being located in the conductor 62.

The pressurestat 59 is arranged to open the switch 60 and stop the motorand compressor when the evaporation or expansion of refrigerant in thecoils I4 is insufficient, either because of reduction of temperature ofthe coils M or reduction of refrigerant supply thereto, to maintain apressure in the expansion or low side of the system above a selected lowpressure for which the pressurestat is set and this pressurestat isarranged to close the switch 50 and start the motor and compressor whenevaporation or expansion is sufficient to cause a selected rise ofpressure in the low side of the system. Thus it will be understood thatby setting the pressurestat for Operation at the appropriate pressure orpressures, the temperature in the compartment may be controlled, or inother words the temperature in the compartment by its influence on therate of evaporation or expansion in the coils l4 controls the operationof the compressor. Moreover, the operation of the compressor is alsoaffected by the rate of supply of liquid refrigerant through theexpansion valve H which in turn is controlled by the bulb I 8 and if thesupply of compressed refrigerant is interrupted, evaporation andexpansion in the coils [4 will cease and through the pressurestat causethe motor and compressor to stop.

In operation of cooling devices'of this character moisture in thecirculated air condenses on the cooled surfaces of the cooling unit and,if the temperature is sufficiently high, drains therefrom into the drainpan, such as the pan 53 shown herein, which is'usually provided for thepurpose.

However, the cooling unit is oftentimes operated at temperaturessufficiently low, at least during part of the operating periods thereof,to cause an accumulation of frost which not only interferes with heattransfer, but obstructs the air passages, and it is necessary to removesuch accumulated frost occasionally. This, as pointed out above, isusually accomplished by shutting down the compressor, for a sufficientlength of time to permit the cooling unit and the air surrounding sameto warm up sufficiently to melt the frost and this not only requires anobjectionable length of time during which normal cooling operation isinterrupted, but exposes the compartment or other space normally cooledby the refrigerating device, to the rise of temperature whichaccomplishes the defrosting and requires prolonged operation of therefrigerating mechanism and extra load thereon, after defrosting, torestore the compartment or other space to the temperature which existedtherein previous to the defrosting operation.

It is for the purpose of avoiding this warming up of the compartment orother space or loss of cool condition therein during defrosting that thecooling unit and fan are enclosed in the heat insulated housing asdisclosed herein, the doors 39 and 42 of which are closed during thedefrosting operation and the interior of the housing thus isolated fromthe compartment I l or other space normally cooled by the refrigeratingdevice so that the warming up for defrosting is confined to therelatively small amount of air in the housing without affecting thetemperature of the air in the compartment II or other space throughwhich the cooled air from the cooling unit I4 is normally circulated bythe fan 28. This isolated small amount of air not only warms up moreeasily and quickly so that the defrosting is accomplished in a muchshorter period of time than previously, but after the defrosting, whenthe doors 39 and 42 are opened, the. amount of warmed air released fromthe housing is insufficient to materially affect the temperature in thecompartment II or other refrigerated space and accordingly since thecool condition of such compartment or space has been substantiallypreserved during defrosting, no prolonged operation of the refrigeratingmechanism or extra load thereon is required after defrosting.

Moreover, to expedite the defrosting, heating elements, preferably ofelectrical type are provided in the housing to heat the air thereinduring defrosting, at which time the fan 28 is operated to circulate theheated air through the cooling unit, and as the doors 39 and 42 areclosed, the air is merely circulated in the housing, the spaces 56 and51 between the heating unit end plates 24 and 25 and the housing sidewalls 31 affording by-passes through which the air discharged by the fanthrough the cooling unit I4 is returned to the rear end of the housingbehind the fan 28 for recirculation through the cooling unit. Preferablythese by-passes 56 and 51 are closed at their forward ends when the door39 is open so as to avoid back draft therethrough during normaldischarge through the front end of the housing, and for this purposeeach by-pass 56 and 51 has a gate 63 at the forward end spring-hinged asat 64 to the forward end of the respective side wall 31-and normallyheld by the spring hinge against the respective cooling unit end plate24 or 25 as shown in Fig. 5 so as to close the respective by-pass 56 or51. For opening these gates 63 when the door 39 is closed an arm 65 isprovided at each lateral edge of the door near the free end thereof andprojects from the inner face of the door so as to swing into the housingas the door 39 is closed and by engagement with the gates 63 force samelaterally against the respective side wall 31 as shown in Fig. 4 inwhich open position said gates 63 are held by said arms 65 while thedoor 39 is closed. Upon opening the door 39 the arms 65 are releasedfrom the gates 63 which then return by the spring tension of theirspring hinges 64 to the closed position against the respective coolingunit end wall 24 or 25.

Preferably a heating element 66 is located at each side of the housinginterior in the space behind the fan 28 as shown in Figs. 1 and 4substantially in the path of the air returning through the by-passspaces 56 and 51, each heating element being mounted on its respectiveside wall 31 by a pair of end brackets 61 which are secured to the sidewall and hold the heating element at a distance therefrom, and eachheating element may have a series of fins 68 thereon to facilitatedissipation of heat therefrom.

These heating elements are energized only while the doors 39 and 42 areclosed, at which time the refrigerating device is stopped so thatcooling of the cooling unit i4 does not occur during the defrostingoperation, and the energizing of the heating elements'and stoppage ofthe refrigerating device are preferably controlled by the closing of thedoors 39 and 42, it being understood, however, that the fan 28 continuesto operate during defrosting.

For controlling the energization of the heating elements 66 and stoppingthe refrigerating device when the doors 39 and 42 are closed, a switch69 may be provided on the side wall 31 of the housing and has a plunger10 which, when the doors 39 and 42 are closed, is engaged by the lever45 to operate the switch. This switch 69, as shown diagrammatically inFig. 8, is of a two way type and controls two circuits from the feedwires H and 12, one of which said circuits leads to a solenoid 13 whichoperates a switch 14 through which current is supplied to the heatingelements 66 and the other of which said circuits leads to a solenoid 75which operates a valve 16 through which liquid refrigerant is suppliedto the expansion valve H, the arrangement being such that in the normalposition of the switch 69 current is supplied to the valve solenoid 15but not to the switch solenoid 13 whereas when the doors 39 and 42 areclosed the switch 69 is operated by engagement of the lever 45 with theplunger 18 so that current is then supplied to the switch solenoid 13but not to the valve solenoid 15. Opening the doors 39 and 42 and therelease of the plunger 18 which thereupon occurs, restores the switch 89to the normal position.

Preferably a thermostatic switch is also provided in the circuit to theswitch solenoid 13 and located in the cooling unit and fan housing, asfor example on the side of the cooling unit as indicated at 11 and setso that the defrosting temperature in the housing does not exceed aselected maximum and preferably also there is a room thermometer in theroom or compartment I l which controls a switch in the circuit to thevalve solenoid for selectively controlling the upper and lower limits ofthe room temperature and this thermometer and switch may be located atany convenient place in the room or compartment as indicated at 18 inFig. 2.

- The valve 16 which is located in the supply pipe-2| through whichliquid refrigerant is sup- 1 plied to the expansion valve |1 closes tointerrupt the supply of refrigerant to the expansion valve unlesscurrent is supplied to theisolenoid 15 which when energized opensthevalve 16 and as the circuit through the switch 88 to the solenoid 15 isclosed when the doors 39- and 42-are open," the solenoid 15 is normallyenergizedand holds the valve 18 open subject, however, to control .bythe room thermometer. and switch 18 which-interrupts the circuit to thesolenoid 15 when the room temperature reaches a selected high and closesthe circuit when the room temperature reaches a selected low.

For purposes of illustration the switch 69 is shown diagrammatically inFig. 8 with the two contacts 19 and 88 with a swinging arm 8|therebetween normally held against the contact 19 by the spring 82 andhaving the plunger 18 attached thereto by which the switch arm BI isswung away from the contact 19 and against the eontact 88 when the lever45 is engaged against said;

' 42 interrupts the supply of current to the solenoid 15, permitting thevalve 16 to close. This interrupts the supply of liquid refrigerant tothe cooling unit l4 and because of the diminished pressure in thecooling unit and throughout the expansion or low side of the systemwhich results from this stoppage of refrigerant supply the pressurestat59 causes the compressor to pump down and stop and to remain inactiveuntil the valve 16 isopened. The closing of the housing doors alsocausescurrent to be supplied to the heating elements 68 and as the fan 28operates while thedoors 39 and 42 are closed, the air which is isolated'in the housing and heated by the heating elements 66 is circulatedthrough the cooling unit l4 and rapidly melts any frost which may haveaccumulated thereon and the resultant water drains down into the pan 53from which it is carried away through the pipe 55. Moreover since thedrain pan 53 and drain pipe 55 are located within the housing with anyoutside portions of the drain pipe insulated, any frost or plunger 10 bythe closing of the doors 39 and 142,

and one of the feed wires, for example the feed wire 12 leads to theswitch arm 8| while the other feed wire 1| leads to the room thermostatand switch 18 which is connected by the'conductor ice which may haveaccumulated in the drain pan or drain pipe is at the same time melted'sothat overflow or stoppage of the drainage facilities is prevented. v

After the defrosting is completed and the frost melted ofi of thecooling unit, the doors 39 and 42 are opened, and this permits return ofthe switch arm 8| to the normal position against the contact 19, therebyinterrupting the supply of current to the solenoid 13 and heatingelements 66 and closing the circuit to the solenoid 15 which opens thevalve'18,-whereupon refrigerant is again supplied to. -the cooling unitl4. and evaporates and expands therein, thus increasing the pressure inthe 83 to the solenoid 15 which has a conductor 84 Y leading therefromto the contact 19 of the switch The other. contact 88 of the switch 89--has a conductor 85 leading tothe vthermostatic switch 11 and from thisswitch a conductor 86 leads to the solenoid 13 from which'aconductor 81leads to the feed wire 1|. A conductor 88 leads from the feed wire 12 tothe heating elements, from which a conductor 89 leads to the conductor81 through the solenoid switch 14 which is closed rent can be suppliedto the heating elements 86,

When, however, the doors 39 and 42 are closed the switch-arm 8| is swungaway from the contact 19 against the contact 88 thereby interruptingcurrent supply to the solenoid 15 and closing the valve 16 until thedoors 39 and 42are again opened and when the switch arm 8| engages theexpansion or low side .ofthe refrigerating system which increasedpressure operates through the pressurestat 59 to start the compressor H5and the normal pressurestat controlled intermittent operation of therefrigerating device is thereby resumed.

' Thus I have not only provided facilities to isolate the zone in whichdefrosting occurs, thereating device is not afiected by the defrosting,it

' contact 88 current is supplied to the solenoid 13 is possible, if. twoor more coolingunit and fan assemblies are employed for cooling suchcompartment or space to continue operation of one or more of theassemblies while one or more of the other assemblies are beingdefrosted.

While I have shown and described my invention in a preferred form, I amaware that various changes and modifications may be made therein withoutdeparting from the principles of my invention, the scope of which is tobe determined by the appended claims.

I claim as my invention:

1. In a refrigerating device, the combination of a heat insulatedhousing having an inlet and an outlet, a, cooling unit and a blower inthe housing between the inlet and outlet, said blower being operable tosupply air to the interior of the housing through the inlet and todischarge the supplied air through the cooling unit and therefromthrough the outlet, doors operable to close the inlet and outlet, one ormore by-passes leading from the discharge side of the cooling unit tothe suction side of the blower to return air discharged-through thecooling unit to the suction side of the blower when the doors areclosed, gates normally closing said by-passes, means on one of the doorsadapted to open said gates when said door is closed, and heating meansin the housing, the operation of which is controlled by the opening andclosing of the doors.

2. In a refrigerating device, the combination of a housing having aninlet and an outlet, a cooling unit in the housing between the inlet andthe outlet, a blower operable to supply air to the interior of thehousing through the inlet and to discharge the supplied air through thecooling unit and therefrom through the housing outlet, a by-pass throughwhich air discharged by the blower through the cooling unit returns tothe suction side of the blower when the doors are closed, and means bywhich the bypass is closed when the doors are open.

3. In a refrigerating device, the combination of a heat insulatedhousing having an inlet and an outlet, a cooling unit and a blower inthe housing between the inlet and outlet, said blower being operable tosupply air to the interior of the housing through the inlet and todischarge the supplied air through the cooling unit and therefromthrough the outlet, doors operable to close the inlet and outlet, one ormore by-passes leading from the discharge side of the cooling unit tothe suction side of the blower to return air discharged through thecooling unit to the suction side of the blower when the doors areclosed, by-pass closing means, heating means in the housing, refrigerantsupply means by which compressed refrigerant is supplied to the coolingunit, and means whereby closing of said doors opens the by-pass closingmeans and starts the heating means and interrupts the supply ofcompressed refrigerant to the cooling unit.

4. The combination with a refrigerator compartment of a combined coolingand defrosting unit mounted therein, said unit comprising a housingsuspended from the top wall of the compartment and having two spacedopenings therefrom communicating with the compartment, eachopeninghaving a door for closing same, said housing containing coolingcoils, a heater and a blower, the heater being operable when the doorsare closed and the blower being operable in both the open and closedpositions of the doors to airculate air in contact with the coils, saidunit being self contained and insertible as a whole with respect to therefrigerator compartment.

5. As a new article of manufacture a self contained cooling anddefrosting unit installable as a whole in a refrigerating compartment,said unit comprising a closed housing with two spaced openings leadingtherefrom, each opening having a, door for closing same, said housingcontaining cooling coils, a heater and a blower, the heater beingoperable when the doors are closed and the blower being operable in boththe open and closed positions of the doors to circulate air in contactwith the coils.

HERMANN J. KRACKOWIZER.

